Implantable and external medical devices are used for a variety of purposes related to treating or monitoring patients. For example, electrical stimulation is recognized as an effective therapy for patients with physical ailments such as chronic pain, movement disorders, gastrointestinal disorders, and pelvic floor disorders. Whether external or implanted, medical devices often deliver electrical stimulation to a patient or monitor the patient via a lead, which may be implanted within the patient.
Implantable leads may be used to place electrodes or sensors at a target location within the patient, e.g., proximate to target tissue, for delivery of stimulation or monitoring. Implantable leads include conductors that couple the electrodes or sensors, typically located near a distal end of the lead, to the medical device at the proximal end of the lead. Typically, leads include at least one conductor per electrode or sensor.
The complexity of leads, e.g., the number of electrodes per lead, has increased. Consequently, the number of conductors within the leads has increased. However, there are problems associated with increasing numbers of conductors within leads, including increased size, decreased flexibility, and an increased propensity for fracture of the conductors or other lead failure. Furthermore, increased numbers of conductors within the lead may increase the size of a header block on an implantable medical device, increasing its overall size, which may be undesirable for implantation.
Use of a switching device, sometimes referred to as a multiplexer (MUX), within the lead has been proposed as a way to avoid the problems associated with increasing numbers of conductors while providing increased numbers of electrodes or sensors on an implantable medical lead. A lead MUX may selectively, e.g., based on control signals from a medical device, couple a smaller number of proximal conductors to a greater number of distal conductors and associated electrodes or sensors. In this manner, the portion of the lead proximal of the MUX may have fewer conductors, and thereby avoid or lessen the problems associated with increased numbers of conductors. The lead MUX may be located relatively distally on the lead, so that a larger, proximal portion benefits from fewer conductors.